sum

Adds up the numbers of a list, or of one field of each entry. An entry that holds nothing is passed over.

Example

const total = sum(order.lines, 'qty')

spent: number({ from: sum({ of: orders, by: 'customer', column: 'total' }) })

Options

Returns

The sum, and 0 for an empty list. Handed one text and nothing else, it answers what group takes for a column, { "sum": "total" }. Handed a reference it answers its record.

In the from of a column, sum({ of, by, where, column }) makes it a column that the engine keeps: the sum of column of the rows of of whose link column by points at the row, and that where names, a filter as a record. The engine moves the number inside the very write that adds, changes or removes such a row, a raw write among them, so it is never late and never drifts, and fills it first by the one walk of the switch that adds the column, a page to a write. No code writes it (code.T2107); it may be filtered, sorted and indexed like any column. It is a fact of the row that holds it, read under that row's rule: it counts every linked row, also those the reader may not read, so a builder who must hide it states read on the column, as read: role('staff'), as on any column. The rows it counts lie in the same data file as its row (code.T2025). The column is a number, from 0.

Errors

code.T0027: a value of another kind than the word works with, or a value past the limit valueSize.

code.T1014: in a from, the column that keeps the sum is no number, or no column is named.

code.T2025: in a from, the counted rows lie in another data file than the row that holds the number.

See also

topic.values, word.avg, word.count